The engine that came in Optra is A16DMS (sometimes referred as A15DMS while the one available in our market is A15MF) which has 1598cc capacity; having 2.5mm larger bore than the 1498cc 1.5L block, other than this there are no big changes. Engine parts like Head, Cams, valve assembly, Cam Gears, Head Gasket, Main pulley timing gear , Timing Guide, Tensioner, Timing Belt, Water Pump, Oil Pump, Crank, Connecting Rod, Piston Pins and Bearings and all the oil seals are the same. Plugs of Optra are also alike.
Two necessary parts are the Plug wires and the filter that are rarely available for which you have to contact Korean parts importers (like Aziz Autos, they need samples which they can import from China/Korea). Optra's plug wires are short in length being distributorless while the filter is 2.5 mm wider.
The estimated costs(dated ~ July 2007) of some of the parts are as follows:
- Timing Belt ~ Rs.3300/=
- Tensioner Bearing ~ Rs.4200/=
- Water Pump ~ Rs.3500/=
- Oil Pump ~ Rs.4500/=
DOHC 16 valve head has more parts than a SOHC head so more wear and tear and more maintenance in term of parts and cost. It is recommmended to change the Timing Belt and Tensioner bearing at the same time and also these items of the Kabli engine must be changed before installing in your car which costs around Rs.7500/=.
The performance of a DOHC 16 valve engine is way better than the SOHC counter part producing ~20N.m. more torque and ~10Kw more power. It is like installing a 2PSi turbo :d.
As far as Tappets are concerned, they are the same Hydraulic ones, so does not need adjustment.
Advanced fuel maps so as a result better petrol consumption while 16 valve head providing better Air suction and as a result better mileage. (Off-course throttle response is better and better mileage can worsen if driven aggressively)
Better road grip, cornering and braking than that of the SOHC. The reason being that the DOHC head is around 12 kg heavier than the SOHC counter part lowering/transferring of weight to the front.
~10% increase in power and torque.
One major drawback ,As @azkhan mentioned, one need to keep an eye on the timing section since breaking a timing belt or the tensioner will result in valve destruction (The valve in SOHC head are opened straight in the cylinders while the DOHC valves are opened at ~ 15 degree angle so in a case of any mishap, the piston directly hit the valve causing them to break due to their angular position.)
One need to have heavy duty high pressure fuel pump to run the engine on petrol properly. The pump of Daewoo is insufficient for the fuel needs.
Ideally CNG Emulator will be required that will disengage the injectors while on CNG.
New parts are bit costly but available.